After Donald Trump visited Moscow in 2013, Russian President Vladimir Putin sent Trump a gift of “a black lacquered box” with something inside — something that remains a mystery to this day, even with Trump now in the Oval Office and Putin accused by United States intelligence agencies of directing a cyber-sabotage and propaganda operation that helped put him there.

That strange revelation comes from an upcoming book about the Russian operation to help elect Trump, Russian Roulette: The Inside Story of Putin’s War on America and the Election of Donald Trump by veteran investigative reporters David Corn of Mother Jones magazine, and Michael Isikoff of Yahoo! News. In an excerpt from the book, published on both news sites Thursday, Corn and Isikoff described that “gift,” given to Trump after the 2013 Miss Universe beauty pageant was held in Moscow. Trump owned the pageant at the time. He brought the event to Moscow for a $20 million fee paid by billionaire real state developer Aras Agalarov, a developer with close ties to Putin.

“Shortly after the Miss Universe event, Agalarov’s daughter showed up at the Miss Universe office in New York City bearing a gift for Trump from Putin,” the book says. “It was a black lacquered box. Inside was a sealed letter from the Russian autocrat. What the letter said has never been revealed.”

The mystery of what the sealed letter contained appears more relevant than ever today, given the seemingly close relationship that has now developed between Trump and the Russian political strongman believed to have helped put him in office. And on Wednesday, Putin himself emphasized that close relationship by openly praising Trump in interviews that aired on Russian state-run television.

“On a personal level he made a very good impression on me,” Putin said in the interviews, as reported by the Associated Press. “I have no disappointment at all.”

Putin went on to describe Trump in terms that may surprise many Americans who have observed Trump since he began running for president in 2015, calling Trump a “balanced” person who makes it “possible to negotiate with him, to search for compromises.”

Putin’s praise of Trump follows years of Trump’s often solicitous attempts to win the Russian leader’s attention, according to Corn and Isikoff. Before traveling to Moscow for the Miss Universe pageant in 2013, Trump posted to his Twitter account, expressing his desire to get into Putin’s good graces, even asking if Putin would become his “best friend.”

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After he returned from Moscow, Trump appeared on David Letterman’s late night talk show, and claimed that he did indeed meet Putin “once,” though, as the Russian Roulette authors note, “in fact, there was no record he ever had.”

Not only had Trump failed to meet Putin, it appears that Putin deliberately snubbed Trump at the 2013 pageant. Trump was in a state of great “anxiety” hoping that Putin would show up at the pageant, according to the book’s account. But as Trump sweated out his wait for the Russian president, Putin sent word that a “Moscow traffic jam” made it impossible for him to make his way to the pageant.

Specifically, Putin claimed that the king and queen of the Netherlands were visiting Moscow and that he was scheduled to meet them, but the traffic jam caused the meeting to run late forcing Putin to opt out of the expected meeting with Trump.

Putin appears to have fabricated that excuse. In fact, he met with the Dutch royal couple on Friday, the day before the pageant. On the day of the event, the king and queen visited an art gallery, met with Russian business leaders, and attended an evening musical performance, according to research by Mother Jones writer Kevin Drum.